Final answer:
The palatoglossus muscle is not innervated by the hypoglossal nerve; instead, it's controlled by the vagus nerve. This is distinct from the other extrinsic tongue muscles like the genioglossus, styloglossus, and hyoglossus, which the hypoglossal nerve innervates.
Step-by-step explanation:
The extrinsic muscles of the tongue include the genioglossus, styloglossus, hyoglossus, and palatoglossus muscles. Each muscle has its own function in facilitating tongue movements crucial for speech and swallowing. Among these, the genioglossus allows the tongue to move downward and forward, the styloglossus enables upward and backward motion, and the hyoglossus facilitates downward and flattening movements.
However, not all of these muscles are innervated by the same nerve. While the hypoglossal nerve is responsible for controlling most of the tongue's muscles, it does not innervate the palatoglossus muscle. Instead, the palatoglossus, which originates on the soft palate and is involved in elevating the back of the tongue, is innervated by the vagus nerve.
Therefore, the correct answer to the student's question is: the palatoglossus muscle is not innervated by the hypoglossal nerve.